The research plan proposes is a series of empirical studies of judgment under uncertainty, in particular the exploration of judgment tasks which involve the use of frequency information to make a decision. There is currently some disagreement in the field of judgment and decision-making as to whether people are capable of making rational choices in these type of judgments, with various groups of researchers predicting that people either can or cannot reason accurately about frequencies and probabilities. A primary goal of this research is to develop and test a simple task for the study of these type of judgments under uncertainty. Also, we seek to determine how the stimulus event information is represented mentally in the participants' memories; here we are especially interested in whether subjects retain information about raw frequencies of occurrence or remember abstracted propensities or relative frequencies. Using this task, we further intend to test a general model of choice under uncertainty, and to use this model in the induction of general principles to predict the conditions under which judgments will be based on absolute or on relative frequencies. Finally, we will implement a neurally-inspired model of the learning, memory, and judgment processes underlying the behavior summarized in this general algebraic model.